Nucleation and Early Stage Crystallization of Fluorapatite in Apatite-Mullite Glass-Ceramics

Abstract

The crystallization morphology and activation energy of fluorapatite formation in apatite-mullite glass-ceramics has been examined. A systematic change in the amount of network modifier in the base glass has demonstrated that increasing levels of network modifier cause a corresponding increase in activation energy for fluorapatite crystallization and a decrease in fluorapatite crystal size. Apatite-mullite glass-ceramics are known to phase separate and nucleate prior to crystallization. To separate these effects during activation energy determination, a nucleation hold was used to ensure the activation energy is purely for crystal growth and is not skewed by any phase separation or nucleation occurring. It is postulated that greater amounts of network modifier in the system cause the base glass to phase separate and nucleate to a greater extent during heating thus limiting the crystal growth.

Nanostructured apatite-mullite glass-ceramics for enhanced primary human osteoblast cell response

“…This composition may produce crystal sizes and spatial density similar to the topographies used by Dalby et al [11]. Some of the glass was re-melted and cast to form cylinders (Ø 11 mm) with annealing at Tg − 100 °C (560 °C) [14]. Cast cylinders were sectioned into 2.5 mm thick discs.…”

“…A glass with molar composition 4.85SiO2-3.25Al2O3-1.5P2O5-3.25CaO-1.75CaF2, chosen following a review of previous studies [14,16,17], was synthesised by melt-quench, as previously described [5,14]. This composition may produce crystal sizes and spatial density similar to the topographies used by Dalby et al [11].…”

“…Glass frit was characterised by differential scanning calorimetry (DSC) [14] to determine the glass transition temperature (Tg) and primary and secondary crystallization peak temperatures (Tp1 and Tp2).…”

“…Such AMGCs offer the potential to create nanoscale topography similar to those presented by Dalby et al [11] by selective etching of the fluorapatite phase at the glass-ceramic surface [14]. However, given that fluorapatite is the phase that is typically etched, the topography is produced by removing the bioactive phase from the surface.…”

The influence of CaF2 content on the physical properties and apatite formation of bioactive glass coatings for dental implants

“…These results were expected as fluoride facilitates crystallization occurrence. However, it has been shown that the activation energy of crystal growth is proportional with increasing CaF 2 content due to its influence on phase separation and nucleation density [25]. The effects of CaF 2 on peak crystallization and sintering windows of glass series are presented in Fig.…”